Foamable styrene polymer particles containing isopentane as the blowing agent and method of making same



March 27, 1962 H. A. WRIGHT 3,027,334

FOAMABLE STYRENE POLYMER PARTICLES CONTAINING ISOPENTANE AS THE BLOWINGAGENT AND METHOD OF MAKING SAME Filed May 19, 1960 L H 0 m n n O A T I.H E "m DU O W 5A5 M I I DE MINEEALIZEP WATER HYDIZOCHLDEIC ACID AC1orrrcmo u (ENTKIFUGATION EXPAH DING:

PETROLEUM ETHER ISOPENTANE- ADDITIVE N PENTANE (WEIGHT PERCENT OFPOLYMER) ALKYL PHENOL POLYOXYETHYLEHES CONDENSATE 1 c 9 b 5 5 J. 1 O 0 OO O ESCAPE OF HYDPOCAPBOHS F ROM POLTSTYEENL &

INVEN TOR. 16/412010 Q. WEIGHT;

DAYS AGED AASY l: is

FOAMABLE STYRENE POLYMER PARTICLES CONTAINING HSUPENTANE AS THE BLOWINGAGENT AND M THO!) F MAKING SAME Harold A. Wright, Beaver, Pa., assignorto toppers Company, inc, a corporation of Delaware Filed May 19, 1960,Ser. No. 30,304 9 Claims. (Cl. 26t)-=2.5)

This invention relates to an expandable thermoplastic material which,under the influence of heat, expands, and when confined during thisexpansion, forms a foamed structure and to the method of preparing theexpandable foam plastic.

The production of expandable thermoplastic materials is well known. Thethermoplastic polymeric materials are rendered expandable by theincorporation in the plastic polymer of from 1% to 5% by weight of asuitable expanding agent. These expandable thermoplastic materials aremade into cellular foam for various useful articles, such as floats,insulation panels, novelties, and cushioning materials such as forpackaging.

It has been recognized that the lower the density of the foam structureproduced from the expandable plastic, the better will be the materialfor uses such as insulation fillers, lightweight aggregate, etc. Effortsto produce low density materials, e.g. less than one pound per cubicfoot, have involved using high percentages of a blowing agent. This hasnot been satisfactory because the cell structure of the expandableparticle has enlarged to such an extent that the general foam structurehas been undesirable. Efforts have also been made to partially expandthe polymeric particles in an unconfined area and thereafter fullyexpanding the particles in a confined area; and this has reduced thedensity somewhat but the desired density of less than one pound percubic foot has been difficult to obtain by this process. Attempts havebeen made to subject the foam structure to further expansion in a steamor otherwise heated atmosphere, and this also has decreased the densityof the foam material but other less desirable physical characteristicsoccurred, for example, changing the cell size so as to give thestructure undesirable characteristics.

It has now been discovered that polymeric material, particularly vinylaromatic polymers having incorporated therein isopentane and analkylphenol polyoxyethylene condensate derived from the reaction productof an alkylphenol having 8 to 12 carbon atoms in the structure andethylene oxide containing from 1 to l0 ethylene oxide units, provide amaterial capable of producing low density cellular foams of fine cellsize. It has been found unexpectedly that the combination of isopentaneand the alkylphenol polyoxyethylene condensate has a synergistic etfectwhen the expendable polystyrene is subjected to heat to provide a foamstructure of low density and fine cell size. The isopentane itselfprovides a cell structure of moderate to large cell size and a densitygenerally greater than one pound per cubic foot in the expandableparticle and the alkylphenol polyoxyethylene condensate by itself has nocharacteristics rates hate ice of causing a foaming action. Isopentaneis incapable of expanding polystyrene to less than one pound per cubicfoot density except with excessively high volatiles or under extremeforced expansion conditions of temperatures and pressure. The inabilityof isopentane to produce foarnable particles of very small cell size isshown in United States Patent No. 2,878,194, where Table I comparesneopentane with isopentane as an expending agent for polystyrene andshows that isopentane itself produces foamable particles of to ,4 (60 tomils) cell size. Thus, the synergistic effect obtained by thecombination of an alkylphenol polyoxyethylene condensate and isopentanein this invention is remarkably demonstrated by the 2 to 6 mil cell sizeand the less than 1 pound per cubic foot density which characterizes thefoamable particles produced therefrom.

In accordance with this invention, polymeric particles capable of beingexpanded into a cellular polymeric structure, are produced by forming anaqueous suspension of particles of a polymer derived from anethylenically unsaturated hydrocarbon monomer and contacting thesuspension with is'opentane having dissolved therein from 5% to 2% ofalkylphenol polyoxyethylene condensate until the solution ofallcylphenol poiyoxyethylene condensate in isopentane is integrated withthe polymer particles, and separating the particles from the aqueousmedium. The alkylphenol polyoxyethylene condensate-isopentane expandingagent is distributed 'substantially throughout the polymeric particles.Thereafter, the polymer particles having said solution of alkylphenolpolyoxyethylene condensate in isopentane expanding agent integratedtherewith, can be individually expanded to produce discrete, cellularparticles having a density of .5 pound per cubic foot. The pre-expandedparticles can be placed in a mold and heated to the softening point ofthe polymer mate ial, whereby the particles, due to exceptionalexpandable properties of the isopentane-alkylphenol polyoxyethyleneexpanding agent, will expand and coalesce into an integral cellularpolymeric structure having superior fusion, low density, and uniformsmall cell size.

The above and further advantages in the novel features of the inventionwill appear more fully from the following detailed description when thesame i read in connection with the accompanying drawing. It is to beexpressly understood, however, that the drawing is not intended as adefinition of the invention, but is for the purpose of illustrationonly.

FIGURE 1 is a how diagram illustrating a preferred method for preparingthe expandable polymeric particles of this invention.

FIGURE 2 is a graph illustrating the escape of hydrocarbon blowing agentfrom representative samples of expandable polystyrene particles.

FIGURE 3 is a graph illustrating the differences in density of variouspartially expanded polystyrene particles.

The particles to be rendered expandable may be vinyl aromatic polymerparticles, such as polystyrene particles, or particles of a copolymer ofstyrene and such monomers as butadiene, alphamethylstyrene, isobutylene,acrylonitrile, vinyl naphtholene, P-isopropylstyrene, ethylhexylacrylate and the like and are impregnated with the volatile aliphatichydrocarbon isopentane containing .5 to 2% of alkyphenol polyoxyethylenecondensate by conventional means, preferably according to the methoddescribed in copending application of G. F. DAlelio, Serial No. 394,230,US. Patent No. 2,983,692. Thereafter, the expandable particles may bepartially expanded by heating, using hot water, steam, infra-red orradio frequency means to produce a partially expanded product of lessthan 1 pound per cubic foot density, capable of further expansion toform a low density foam of opaque appearance having uniform small cellsthroughout.

For purpose of comparison, polystyrene was impregnated with severalexpanding agents and with alkylphenol polyoxyethylenecondensate-isopentane expanding agent in accordance with the processdescribed in copending application of G. F. DAlelio, Serial No. 394,230,to form expandable polystyrene. This expandable polystyrene was foamedin accordance with the process described in Stastny Patent No. 2,787,809and the products were measured for cell diameter. The results were asfollows in Table I:

TABLE I Cell size, mils Modified isopentane 2-6 N-pentane l30Normal-hexane 30-50 Petroleum ether 10-30 Surprisingly, the expandingagent of my invention had the smallest average cell size. It is mostremarkable, when compared with Table I of United States Patent No.2,878,194, in which unmodified isopentane was shown, to yield productsof cell size of A to /s" (60-120 mils).

The escape of hydrocarbon blowing agent from the polymer particle inwhich it is incorporated, is a measure of the usefulness of theexpandable product (the slower the escape of expanding agent from theexpandable material, the better commercial utility the expandablematerial will have). For purposes of evaluating my product with thoseproducts produced from other expanding agents, a series of tests weremade. Approximately 60 grams each of dry impregnated particles wereplaced in a pound size Kraft bag which was folded twice at the top andstapled. The samples so stored were allowed to age at ambient roomconditions (23 C.-25 C.) for a prolonged time. Periodically, the beadswere shaken, representative samples were removed for total volatileanalysis and the bag resealed for further aging. The total volatileswere plotted against days of aging to yield the results shown in FIGURE2.

The expanding agent is prepared by dissolving .5 to 2% by weight of analkylphenol polyoxyethylene condensate in isopentane at about 25 C. Atleast .5% of the polyoxyethylene condensate is necessary to give thesynergistic expanding power whereas when additive in amounts greaterthan 2% by weight are added to the isopentane expanding agent, excessiveshrinkage and an undesirable increase in density of the product occurs.

The additive used in the novel expansion system of this invention is analkylphenol polyoxyethylene condensate consisting of an alkylphenolhaving 8 to 12 carbon atoms in the alkyl chain, which alkylphenol iscondensed with from 1 to molecules of ethylene oxide. Typical examplesof the alkylphenol polyoxyethylene condensates which may be employed inthis invention include isooctylphenol-ethylene oxide (1:3),nonylphenolethylene oxide (1:2), dodecylalcohol-ethylene oxide (1:5).

The ethylene oxide units of the typical additives may 4 range from 1 to10 units average composition. If the condensate contains more than 10ethylene oxide units, the condensate is not completely soluble in theisopentane, and therefore, the greater number of ethylene oxide units isof no practical value to this expansion system.

The isopentane which is used as the volatile aliphatic hydrocarbon maybe commercial grade which boils within the range of 24 C. to 32 C. Thealkylphenol polyoxyethylene condensate isopentane foaming agent iscapable of being integrated with the particular polymeric material beingtreated without causing agglomeration or precipitation from thesuspension.

The following, which for purposes of ease in explanation, is termedExample I, will illustrate a manner in which the invention may becarried out.

Example I To a 100 gallon kettle equipped with a stirrer, 122 parts byweight of demineralized water, .035 part by weight of dodecyl benzenesulfonate (Nacconol NRSF) and 1.04 parts by weight of tricalciumphosphate, was charged successively with agitation. The vessel was thencharged with 100 parts of polystyrene particles (sold under the tradename Dylene 8); 1.25 parts of isooctylphenol-ethylene oxide condensate(3 ethylene oxide units) was dissolved in 11 parts by weight ofisopentane in a separate calibrated mix tank at about 25 C. The aqueoussuspension of polystyrene particle was heated to 60 C. and the vessel ispurged free of air with inert gas. The solution ofisooctylphenol-ethylene oxide in isopentane was fed to the impregnationvessel at a constant rate over 1.5 hour period. The impregnation vesselwas heated from 60 C. to 90 C. over a .5 hour period. The vessel wasmaintained at 90 C. for a total of ten hours. The pressure in the vesselat the start of this ten hour period was 86.5 p.s.i.g. and at the end ofthe period, was about 58 p.s.i.g. The vessel was cooled to 25 C. to 28C., and the suspension was transferred into a wash kettle. Hydrochloricacid was added to the impregnation slurry to lower the slurry pH from6.5 to 1.2-1.0 and is to dissolve the calcium phosphate from the surfaceof the bead product. Thereafter, the beads were passed through acontinuous centrifuge and washed with about 2.0 gallons of wash waterper pound of product at a temperature of about 15 C. to 25 C., to ridthe bead surface of residual Nacconol.

The washed heads (5% surface moisture, nil internal moisture) are passedthrough a continuous rotary dryer maintained at 120 F. to 125 F. andthen conveyed to a storage bin, from where they were screened andpackaged. The impregnated beads contained 7.5 to 8.0 percent by weightof volatiles.

Dried expandable particles made as above may be heated immediately aftermanufacture, using conventional means such as described on page 19 ofthe Koppers Company, Inc. booklet entitled Dylite ExpandablePolystyrene, to make low density foam, i. e., one having a density of .5pound per cubic foot, or they may be stored for an indefinite period forthe production of a foamed article at a later date. The particles may bepartially expanded to produce an integral, free-flowing, low densityproduct from which only a portion of the aliphatic hydrocarbon has beenvolatilized. Such partially expanded particles are quite suitable formolding purposes. The partially expanded particles may be stored orfurther expanded by the application of heat to make an integral, lowdensity opaque foam having uniform small cells.

Using the procedure of Example I, expandable polystyrene was producedusing various alkylphenol polyoxyethylene condensates in isopentane. Theresults are tabulated below as Table II.

TABLE II ALKYLFHENOL-ETHYLENE OXIDE (ETO) OONDENSATES Expansion and FoamStructure of Additive, Partially Expanded Particles Ethylene OxideSolubility Percent Total Alkyl Identity (Moles Type of Volatiles BoilingWater 3 Minutes Steam 10 Minutes per mole Polymers of alkylphenol)Density Shrinkage Cell Density Shrinkage Cell Size Size None... 6.691.50 0. 6. 58 0. 95 1.0 6. 65 0.86 1. 5 6. 78 0.78 2. O 6. 97 0. 90 3.07. 21 1.09 None- 6. 69 1. 50

In the above table, total volatiles were determined by subjecting onegram of the dry impregnated particles to a temperature of 150 C. for oneand one-half to two hours and measuring the loss in weight as a percentof the original weight of dry beads.

The expansion characteristics of the impregnated polystyrenes weredetermined by (l) immersion of the beads in boiling water for threeminutes, and (2) exposure of the beads to steam at atmospheric pressurefor ten minutes. The bulk density of the resultant expanded particles,which value directly determines the density of any article moldedtherefrom, was determined.

The appearance of expanded foams was evaluated in the individualpartially expanded beads considering (1) shrinkage, and (2) the averagesize of the cells. Item 1 was determined by straightforward visualobservation. Cell size was determined microscopically, using a projectedstage micrometer scale to measure the approximate cell diameters. Tothis end, the partially expanded head was sliced into two hemispheresand a wedge-like, semicircular wafer whose straight edge formed the apexof the wedge, was cut from one hemisphere. This wafer was viewed under50X magnification, the image being superimposed on the projected scaleabove to permit direct measurement of the various cells along the baseof the semi-circle. By having the apex of the wedge coincide with thisbase, interference from shadows of other cells behind the one beingmeasured was avoided. The range of values recorded in the chartrepresent the majority of cells along the base.

The foamed products made from these novel particles are useful asinsulated building panels, floats, decorative display objects, noveltiesand toys. The ability to expand to low densities in a given volume makesthe use of the particles economically advantageous for all applicationswhere lightweight foamed objects are of interest.

What is claimed is:

1. A foamable polystyrene particle containing substantially uniformlydistributed throughout isopentane and an alkylphenol polyoxyethylenecondensate derived from the reaction product of an alkylphenol having 8to 12 carbon atoms in the alkyl chain with ethylene oxide, said alkylphenol polyoxyethylene condensate containing from 1 to ethylene oxideunits in the polyoxyethylene portion, which polymer particle uponheating will expand to a structure of less than one pound per cubic footdensity having uniformly small cells.

2. A foamable styrene polymeric particle containing substantiallyuniformly throughout a solution of an alkylphenol polyoxyethylenecondensate derived from the reaction product of an alkylphenol having 8to 12 carbon atoms in the alkyl chain with ethylene oxide, said alkylphenol polyoxyethylene condensate containing from 1 to 10 ethylene oxideunits in the polyoxyethylene portion in isopentane to provide from 5 to15 percent of isopentane and from about .5 to 2 percent of analkylphenol polyoxyethylene condensate derived from the reaction productof an alkylphenol having 8 to 12 carbon atoms in the alkyl chain withethylene oxide, said alkyl phenol polyoxyethylene condensate containingfrom 1 to 10 ethylene oxide units in the polyoxyethylene portion in saidparticle which particle upon heating will expand to a structure of lessthan one pound per cubic foot density having uniformly small cells.

3. Foamable styrene polymeric particles which upon heating will expandto a structure of less than one pound per cubic foot having uniformlysmall cells produced by forming in an aqueous medium a suspension ofparticles of a polymer obtained by polymerizing an ethylenicallyunsaturated hydrocarbon monomer, selected from the group consisting ofstyrene, butadiene, alphamethylstyrene, isobutylene, acrylonitrile,vinyl naphthalene, P- isopropylstyrene, 2 -ethylhexylacry1ate andmixtures thereof, contacting said suspension with a solution of analkylphenol polyoxyethylene condensate derived from the reaction productof an alkylphenol having 8 to 12 carbon atoms in the alkyl chain withethylene oxide, said alkyl phenol polyoxyethylene condensate containingfrom 1 to 10 ethylene oxide units in the polyoxyethylene portion inisopentane, until said solution is integrated with said particles, andseparating said particles from the aqueous medium.

4. A foamable styrene polymer particle containing substantiallyuniformly distributed throughout isopentane and an alkylphenolpolyoxyethylene condensate derived from the reaction product of analkylphenol having 8 to 12 carbon atoms in the alkyl chain with ethyleneoxide, said alkyl phenol polyoxyethylene condensate containing from 1 to10 ethylene oxide units in the polyoxyethylene portion which polymerparticle upon heating will expand to a structure of less than one poundper cubic foot density having uniformly small cells.

5. Foamable polystyrene particles which upon heating will expand to astructure of less than one pound per cubic foot having uniformly smallcells produced by forming in an aqueous medium a suspension of particlesof a polymer obtained by polymerizing an ethylenically unsaturatedhydrocarbon monomer selected from the group consisting of styrene,butadiene, alphamethylstyrene, isobutylene, acrylonitrile, vinylnaphthalene, P-isopropylstyrene, Z-ethylhexylacrylate and mixturesthereof contacting said medium with a solution of an alkylphenolpolyoxyethylene condensate derived from the reaction product of analkylphenol having 8 to 12 carbon atoms in the alkyl chain with ethyleneoxide, said alkyl phenol polyoxyethylene condensate containing from 1 to10 ethylene oxide units in the polyoxyethylene portion in isopentaneuntil said solution is integrated with said particles, and separatingsaid particles from the aqueous medium.

6. A foamable styrene polymeric particle containing substantiallyuniformly distributed throughout a solution of alkylphenolpolyoxyethylene condensate derived from the reaction product of analkylphenol having 8 to 12 carbon atoms in the alkyl chain with ethyleneoxide, said alkyl phenol polyoxyethylene condensate containing from 1 to10 ethylene oxide units in the polyoxyethylene portion in isopentane toprovide from to 15 parts of isopentane and 1.25 parts of an alkylphenolpolyoxyethylene condensate derived from the reaction product of analkylphenol having 8 to 12 carbon atoms in the alkyl chain with ethyleneoxide, said alkyl phenol polyoxyethylene condensate containing from 1 toethylene oxide units in the polyoxyethylene portion in said particlewhich particle upon heating will expand to a structure of less than onepound per cubic foot density having uniformly small cells.

7. A method for the production of foamable styrene polymeric particleswhich upon heating will expand to a structure of less than one pound percubic foot having uniformly small cells which comprises forming in anaqueous medium a suspension of particles of a polymer obtained bypolymerizing an ethylenically unsaturated hydrocarbon monomer, selectedfrom the group consisting of styrene, butadiene, alphamethylstyrene,isobutylene, acrylonitrile, vinyl naphthalene, P-isopropylstyrene, 2-ethylhexylacrylate and mixtures thereof contacting said suspension withisopentane having dissolved therein an alkylphenol polyoxyethylenecondensate derived from the 8 reaction product of an alkylphenol having8 to 12 carbon atoms in the alkyl chain with ethylene oxide, said alkylphenol polyoxyethylene condensate containing from 1 to 10 ethylene oxideunits in the polyoxyethylene portion until said solution is integratedwith said particles, and separating said particles from the medium.

8. A method for the production of foamable styrene polymeric particleswhich particles upon heating will expand to a structure of less than onepound per cubic foot density having uniformly small cells comprisesintegrating isopentane having dissolved therein an alkylphenolpolyoxyethylene condensate derived from the reaction product of analkylphenol having 8 to 12 carbon atoms in the alkyl chain with ethyleneoxide, said alkyl phenol polyoxyethylene condensate containing from 1 to10 ethylene oxide units in the polyoxyethylene portion, with a polymerobtained by polymerizing an ethylenically unsaturated hydrocarbonmonomer selected from the group consisting of styrene, butadiene,alphamethylstyrene, isobutylene, acrylonitrile, vinyl naphthalene,P-isopropylstyrene, 2- ethylhexylacrylate and mixtures thereof.

9. A method for the production of foamable styrene polymeric particleswhich particles upon heating will expand to a structure of less than onepound per cubic foot density having uniformly small cells whichcomprises integrating 5 to 15 parts of isopentane having dissolvedtherein .5 to 2 parts of an alkylphenol polyoxyethylene condensatederived from the reaction product of an allcylphenol having 8 to 12carbon atoms in the alkyl chain with ethylene oxide, said alkyl phenolpolyoxyethylene condensate containing from 1 to 10 ethylene oxide unitsin the polyoxyethylene portion with a polymer obtained by polymerizingan ethylenically unsaturated hydrocarbon monomer selected from the groupconsisting of styrene, butadiene, alphamethylstyrene, isobutylene,acrylonitrile, vinyl naphthalene, P-isopropylstyrene,Z-ethylhexylacrylate and mix tures thereof.

No references cited.

1. A FOAMABLE POLYESTYRENE PARTICLE CONTAINING SUBSTANTIALLY UNIFORMLYDISTRIBUTED THROUGHOUT ISOPENTANE AND AN ALKYLPHENOL POLYOXYETHYLENECONDENSATE DERIVED FROM THE REACTION PRODUCT OF AN ALKYLPHENOL HAVING 8TO 12 CARBON ATOMS IN THE ALKYL CHAIN WITH ETHYLENE OXIDE, SAID ALKYLPHENOL POLYOXYETHYLENE CONDENSATE CONTAINING FROM 1 TO 10 ETHYLENE OXIDEUNITS IN THE POLYOXYETHYLENE PORTION, WHICH POLYMER PARTICLE UPONHEATING WILL EXPAND TO A STRUCTURE OF LESS THAN ONE POUND PER CUBIC FOOTDENSITY HAVING UNIFORMLY SMALL CELLS.